In telecommunication switching systems utilizing digital transmission, it is common practice to multiplex a plurality of PCM encoded analog speech signals onto a common data transmission path. The PCM encoded signals are coupled through the digital switching system where they are distributed in accordance with address control information. Due to the high reliability requirements of such systems, it is also common practice to duplicate all major networks of the system or to provide sufficient capacity that should one section fail another can take over with the only penalty being some loss of access to the system during busy periods.
In the past, time division multiplexed PCM (pulse-code-modulation) data has been distributed from the switching system to a plurality of line circuits over a common bus system utilizing address control to access each line circuit during its assigned time slot. A major weakness of such a system is that should the input to one of the line circuits develop a short circuit, the whole bus including the balance of the line circuits connected to it, is rendered unserviceable even though redundant components feeding the bus system have been provided.